1. Field of the Invention
The present invention relates to a field weakening control apparatus for a permanent magnet motor and electric power steering using the same.
2. Description of the Related Art
As to a conventional technique related to phase control in a weakened field region, in JP 2005-110354A, there is described a method which gives a speed control unit an instruction to lower a current reference based on a voltage phase angle, thereby limiting the current reference to control a voltage phase.
However, in the method of that Publication, variation in power supply voltage, variation in frequency, and variation in inductance are not taken into account, and hence maximum torque (limit torque) that the motor can output cannot be output.